not seeing USB key

[piscvau]

Hello
I am using Oracle Virtual box version 4.3.20. The host is Xubuntu 14.04 LTS. The guest is windows XP 32 bits. The USB is configured in the VM machine.
I chexked in Windows and it says that the USB device pilot is OK.
I have a 4GO standard USB key. When I insert it in the machine the host detects it and reads its content. I start the VM Windows XP and the USB key at the bottom of the screen is green for a little. If I go in the windows explorer I do not see the USB key. In the menu I click peripherals USB and it says no peripheral is connected.

I tried it the other way around: no USB key is in. I start the Windows XP machine. I insert the USB key. My thunar file handler window pops up in the host machine. At the bottom of the screnn the USB light becomes green for a short tim. Nothing happens in the WIndows XP machine. If I click on peripheral USB ti says no USB device is connected.

Can anyone help?